Putintseva took on the American in Indian Wells this year and forced a tie-break in the opening set before being overwhelmed in the second.

The 21-year-old said: "Of course she's the best player. She's a legend. I'm just going to go there and show my game, show my best, and we'll see what's going to happen. I have nothing to lose obviously against her."

Williams has yet to drop a set on clay this season, but a woman in almost as good form is Kiki Bertens, who added 15th seed Madison Keys to her list of scalps.

Bertens won the title in Nuremberg the week before Roland Garros as a qualifier and has won 11 straight matches.

Both Simona Halep and Eugenie Bouchard followed up winning the title in Nuremberg with long runs in Paris in the last few years, and Dutchwoman Bertens said with a smile: "M aybe there is something in the food there. I have no idea.

"I felt good there that week. I'm coming here with a lot of confidence. I'm still playing here. It's just amazing for me."

On Thursday, Bertens meets eighth seed Timea Bacsinszky, who defeated Venus Williams 6-2 6-4 to deny the veteran American a first quarter-final appearance at Roland Garros in 10 years.

Bacsinszky's run to the semi-finals 12 months ago was a big surprise but that is not the case this year.

Venus, meanwhile, had sympathy for Halep and Agnieszka Radwanska, who both suffered upsets on Tuesday and were furious at having been made to play in the rain.

"I think the conditions were not playable yesterday," said Venus.

"It was really bad. It's hard to see. The balls are wet, the courts are wet. I wasn't out there the whole time that some of the matches were on, but it just seemed terrible.

"It should be fair. Some players shouldn't have to play in that weather and others not."